115
7
Opiate content can vary in different cultivars of the opium poppy but also between
different species of the Papaveraceae. Species such as P. bracteatum, which have a low
morphine and codeine content, are used for the isolation of thebaine, a precursor for the
manufacture of semisynthetic and synthetic opioids (Vincent et al. 1977). Targeted mutations such as in the thebaine oripavine poppy 1 (top1) variety, which infer a block of morphine biosynthesis, lead to the accumulation of thebaine and oripavine, but not morphine
or codeine (Millgate et al. 2004) and are also used for biotechnological applications.
Opioids of different chemical origin can be found in other plants. For example, salvinorin A, a highly oxidized diterpenoid, is the main active psychotropic compound in
Salvia divinorum (Ortega et al. 1982). Sage of the diviners, also called seer’s sage, is
endemic to a relatively small region in the mountainous north-eastern corner of the
Mexican state of Oaxaca and has a long history of use as an entheogen by Mazatec shamans (Valdés et al. 1987). Salvinorin A acts as a κ-opioid receptor agonist and is the first
known non-alkaloid compound acting on this receptor (Roth et al. 2002). Salvia divinorum synthesizes and excretes salvinorin A via glandular trichomes that are distributed over
much of the plant’s exterior suggesting that they serve a protective function, but as with
morphine, the exact role of this compound for the plant is not known.
Take-Home Messages
5 Classical GPRCs do not seem to exist in plants, but many plant-derived drugs
target GPCRs in animals and humans.
5 Opioids such as morphine and salvinorin A are the best described secondary
metabolites acting on the opiate receptor. The function for the plant is not
known, but protection against mechanical damage could be one role of morphine.
5 Several phytocannabinoids affect the human cannabinoid receptors, the best
known being THC. In addition to antimicrobial activity, it might also provide
protection from UV damage.
5 Atropine, scopolamine and acorine are plant-derived drugs that target muscarinic acetylcholine receptors. Some animals are insensitive to atropine poisoning, including bees, which can accumulate in their honey when they pollinate
Atropa belladonna.
5 Caffeine, an antagonist of the adrenic receptor, is probably the plant-derived
psychoactive drug with the widest use worldwide. It has multiple other cellular
targets including the ryanodine receptor and the enzyme phosphodiesterase.
While toxic to many animals, it can improve the reward memory of bees,
thereby increasing pollination probability. In addition, caffeine released in the
soil causes allelopathic effects that might help the coffee plant to compete
with other plants.
5 No plant-derived drug is known to directly target the dopamine receptor, but
compounds such as cocaine affect dopamine signalling by inhibiting the dopamine transporter. In the field, coca plants are mostly pest free indicating that a
likely role of cocaine is protection against herbivores and pathogen.
5 Mescaline is the only plant-derived drug known to target the 5HT2A receptor
since the best- known compound, ergotamine, is made by fungi-infecting the
plants. However, nothing is known about the role of mescaline for the plant.
7.7 · Opioid Receptor: Morphine/Opiates and Opioids
7
Opiate content can vary in different cultivars of the opium poppy but also between
different species of the Papaveraceae. Species such as P. bracteatum, which have a low
morphine and codeine content, are used for the isolation of thebaine, a precursor for the
manufacture of semisynthetic and synthetic opioids (Vincent et al. 1977). Targeted mutations such as in the thebaine oripavine poppy 1 (top1) variety, which infer a block of morphine biosynthesis, lead to the accumulation of thebaine and oripavine, but not morphine
or codeine (Millgate et al. 2004) and are also used for biotechnological applications.
Opioids of different chemical origin can be found in other plants. For example, salvinorin A, a highly oxidized diterpenoid, is the main active psychotropic compound in
Salvia divinorum (Ortega et al. 1982). Sage of the diviners, also called seer’s sage, is
endemic to a relatively small region in the mountainous north-eastern corner of the
Mexican state of Oaxaca and has a long history of use as an entheogen by Mazatec shamans (Valdés et al. 1987). Salvinorin A acts as a κ-opioid receptor agonist and is the first
known non-alkaloid compound acting on this receptor (Roth et al. 2002). Salvia divinorum synthesizes and excretes salvinorin A via glandular trichomes that are distributed over
much of the plant’s exterior suggesting that they serve a protective function, but as with
morphine, the exact role of this compound for the plant is not known.
Take-Home Messages
5 Classical GPRCs do not seem to exist in plants, but many plant-derived drugs
target GPCRs in animals and humans.
5 Opioids such as morphine and salvinorin A are the best described secondary
metabolites acting on the opiate receptor. The function for the plant is not
known, but protection against mechanical damage could be one role of morphine.
5 Several phytocannabinoids affect the human cannabinoid receptors, the best
known being THC. In addition to antimicrobial activity, it might also provide
protection from UV damage.
5 Atropine, scopolamine and acorine are plant-derived drugs that target muscarinic acetylcholine receptors. Some animals are insensitive to atropine poisoning, including bees, which can accumulate in their honey when they pollinate
Atropa belladonna.
5 Caffeine, an antagonist of the adrenic receptor, is probably the plant-derived
psychoactive drug with the widest use worldwide. It has multiple other cellular
targets including the ryanodine receptor and the enzyme phosphodiesterase.
While toxic to many animals, it can improve the reward memory of bees,
thereby increasing pollination probability. In addition, caffeine released in the
soil causes allelopathic effects that might help the coffee plant to compete
with other plants.
5 No plant-derived drug is known to directly target the dopamine receptor, but
compounds such as cocaine affect dopamine signalling by inhibiting the dopamine transporter. In the field, coca plants are mostly pest free indicating that a
likely role of cocaine is protection against herbivores and pathogen.
5 Mescaline is the only plant-derived drug known to target the 5HT2A receptor
since the best- known compound, ergotamine, is made by fungi-infecting the
plants. However, nothing is known about the role of mescaline for the plant.
7.7 · Opioid Receptor: Morphine/Opiates and Opioids